Ten-year Update of Limited Maintenance Plan for PM10; State of Arizona; Payson

Technical Support Document 

January 2, 2014

U.S. EPA Region 9
1

Background

On August 9, 2001, EPA issued guidance on streamlined maintenance plan provisions for certain 

moderate PM10 nonattainment areas seeking redesignation to attainment (Memorandum from 

Lydia Wegman, Director, Office of Air Quality Planning and Standards, to Directors of EPA 

Regional Air Programs entitled "Limited Maintenance Plan Option for Moderate PM10

Nonattainment Areas" (“LMP Policy”)). This policy allows maintenance plans for areas having a 

low risk of future exceedances of the PM10 standard to forego air quality modeling, future year 

emission inventories, and some of the standard analyses used to determine transportation 

conformity with the SIP. 

In order to qualify for the LMP option, the area should be maintaining the NAAQS, and the 

average PM10 design value for the area, based upon the most recent five years of air quality data 

at all monitors in the area, should be at or below 40 ug/m3for the annual and 98 ug/m3for the 24 

hour PM10 NAAQS with no violations at any monitor in the nonattainment area. (See section IV 

of the LMP Policy.) The 40 and 98 ug/m3limits are margin of safety (MOS) limits for the 

relevant PM10 standard for a given area.1In addition, the area should expect only limited growth 

in on-road motor vehicle PM10 emissions (including fugitive dust) and should have passed a 

motor vehicle regional emissions analysis test.

The LMP Policy also states that once the LMP option is in effect, the state must verify in each 

subsequent year that it still qualifies for the LMP option by recalculating the area’s average 

design value annually and determining that the LMP criteria are met for that year. If they are not 

met, the state should act to reduce emissions enough to requalify for the LMP option, for 

example, by using a contingency measure or other SIP-approved measure. If the attempt fails, or 

succeeds but there is an additional failure in the future, the LMP is no longer in effect and a full 

maintenance plan would need to be developed.2

The Payson PM10 maintenance area originally qualified for the LMP option in 2002. In order to 

continue to qualify, the State must demonstrate that Payson met the requirements of the LMP 

Policy for the ten-year period after it qualifies for the LMP, and will continue to meet the criteria 

in the next ten years. 

Evaluation

Based on our evaluation of the 2011 Payson LMP update, annual reports, and supporting 

documentation, and for reasons stated in the Direct Final Rule Notice and in this technical 

support document (TSD), we find that Payson, AZ continues to meet the requirements of the 

LMP Policy, and is expected to meet the LMP requirements in the next ten years. EPA’s Federal 

Register notice for this submission contains the analysis supporting approval of the ten-year 

 

1 On October 17, 2006 EPA revoked the annual PM10 NAAQS (71 FR 6144). Therefore, the requirement for the 

average annual design value for the margin of safety is no longer applicable.

2 LMP Policy, 2001, p 3.
2

update of the LMP Plans. The following analysis supplements the information in the Federal 

Register notice for this action. None of the information or recommendations in this TSD affect 

our decision to approve the Payson LMP update.

1) Data Completeness

The data recovery standard of 75%, which is required by 40 CFR 50 Appendix K (2.3)(a), was 

met every quarter during the LMP ten-year update period with the exception the 1

st quarter of 

2005, where the data were 47% complete (7 of 15 samples).

3

 Six samples were not used due to a 

lab weighing problem. One was excluded due to under-sampling, and another due to oversampling.

4

EPA guidance allows for data substitution for missing samples when the data are less 

than 75% complete. 5In this case, EPA is using its discretion to allow data substitution for the 

following reasons: 1) EPA takes into consideration that the data recovery was 75% or more in 

every other quarter during the LMP ten-year update period; 2) Payson met the LMP Design 

Value or Critical Design Value requirements in every quarter of the ten-year update period; 3) 

There appear to be no distinct seasonal patterns to the data provided in the annual reports to 

indicate that the 1st quarter would tend to have higher 24-hour maximum sample values than 

other quarters in the year;

6

and 4) Maximum readings in the 1st quarter have decreased over time 

since 2005. We have no data or other basis to indicate that the missing data in the 1st quarter of 

2005 negatively affected the ability of the area to maintain the LMP status, or to continue to do 

so in the future.

2) Calculation of five-year design values

To continue to qualify for the LMP, the LMP Policy states the following: “The area should be 

attaining the NAAQS and the average PM10 design value for the area, based upon the most 

recent five years of air quality data at all monitors in the area, should be at or below 40 ug/m3for 

the annual and 98 ug/m3for the 24-hr PM10 NAAQS with no violations at any monitor in the 

nonattainment area.” (LMP Policy pp. 2-3). Footnote 4 on page 3 of the LMP Policy states that 

“The methods for calculating design values for PM10 are presented in a document entitled the 

“PM10 SIP Development Guideline”, EPA-450/2-86-001, June 1987. The State should determine 

the most appropriate method to use from this Guideline in consultation with the appropriate EPA 

Regional office staff.” Based on the most recent five years of air quality data, the Payson area

meets these criteria. 

 

3 Maintenance of the PM10 NAAQS and Limited Maintenance Plan design values for the Payson PM10 maintenance 

area – 2001-2005, letter from Stephen A. Owens, Arizona Department of Environmental Quality to Wayne Nastri, 

EPA Regional Administrator, Enclosure 2, June 7, 2006.

4 Email correspondence from John Englander, ADEQ to Wienke Tax, EPA, June 17, 2013.

5 Guideline on Exceptions to Data Requirements for Determining Attainment of Particulate Matter Standards, U.S. 

Environmental Protection, April 1987.

6 Email correspondence from John Englander, ADEQ to Nancy Levin, EPA, July 16, 2013.
3

We note, however, that over the ten-year update period, ADEQ was not consistent in how it 

calculated the five years of data. ADEQ used the maximum of the most recent five three-year 

DVs for the annual recertification of LMP status for the years 2003, 2004, 2005, 2006, 2007 and 

2011.

7

For the 2008 certification, ADEQ used the maximum three-year DV for the most recent 

three years, rather than the most recent five years. Because the data used to calculate each of the 

three-year DVs covered the five years (2004-2008), they meet the LMP DV criterion. For 2010, 

ADEQ used the highest max sample -- 66 ug/m3-- for the five-year period (2004-2010).

8 ADEQ 

did not submit an annual report for the year 2009, however, the annual reports for 2008 and 2010 

contain the data needed to confirm that the Payson area was well below the LMP limits for the 

five-year criterion. EPA used data in the LMP reports to calculate the five-year DV using each of 

the above methods for each of the ten years, and in all cases, Payson would have qualified as 

below the LMP DV criterion. While ADEQ’s interpretations did not result in a material 

difference in our decision, we recommend that for future use of the LMP Policy, States use a 

consistent method for calculating the five-year DV for PM10 24-hour standard.

3) Residential Wood Combustion value

The emissions inventory in LMP Update Table 3.5 shows Gila residential wood combustion

emissions as 53 tons per year (tpy), based on 2008 NEI data. However, the 2008 NEI for Gila 

Fuel-Comb-Residential-Wood is 61.6 tpy. When the population ratio of 0.3 is applied to scale 

the number to the Payson area,

9

the result is 18.5, which exceeds ADEQ’s estimated value by of 

15.9 by 2.6 tons. The calculation would only slightly increase the percentage of Residential 

Wood Combustion relative to the other categories of sources.

10 We point this out only as an 

inconsistency, and it does not affect our decision to approve the LMP.

4) Industrial sources

The LMP states that the emissions data for 2008 from industrial sources were provided to 

ADEQ “in response to an annual survey conducted by ADEQ” (see Section 3.2.2, p. 10). In a 

 

7 Maintenance of the PM10 NAAQS and Limited Maintenance Plan design values for the Payson PM10 maintenance 

area – 1999-2003, dated October 6, 2005, Enclosure 1 page 4; Maintenance of the PM10 NAAQS and Limited 

Maintenance Plan design values for the Payson PM10 maintenance area – 2000-2004, dated October 6, 2005, 

Enclosure 1 page 4; Maintenance of the PM10 NAAQS and Limited Maintenance Plan design values for the Payson 

PM10 maintenance area – 2001-2005, dated June 7, 2006, Enclosure 1 page 4; Maintenance of the PM10 NAAQS and 

Limited Maintenance Plan design values for the Payson PM10 maintenance area – 2002-2006, dated June 7, 2007, 

Enclosure 1 page 4; Maintenance of the PM10 NAAQS and Limited Maintenance Plan design values for the Payson 

PM10 maintenance area –2003-2007, dated July 11, 2008, Enclosure 1 page 3; 2012 Limited Maintenance Plan 

Annual Report for the Payson PM10 Maintenance Area, dated September 6, 2012, Enclosure 1.

8

2011 Update of the Limited maintenance Plan for the Payson PM10 Maintenance Area, Figure 4.1, January 23, 

2012.

9

Final Update to the Limited Maintenance Plan for the Payson PM10 Maintenance Area, December 2011, page 10.

10 The percentage would change from 4.6 to 5.4 of the total Payson emissions inventory.
4

conversation with EPA on July 2, 2013, ADEQ clarified that the data was compiled by ADEQ 

from emission reports that are required of all permitted major and minor sources in the area.11

5) Control measures in the 2002 LMP

In a conversation with EPA on July 2, 2013, ADEQ clarified that the LMP ten-year updates do 

not rely on additional control measures to continue to maintain the NAAQS for PM10 and that the 

LMPs have not revised these measures.12

6) Limited Growth

In order to continue to qualify for the LMP, the area must pass a test using a motor vehicle 

regional analysis methodology to determine whether increased growth in the area would threaten 

the assumption of maintenance that underlies the LMP policy.13 To have an acceptable margin of 

safety (i.e. pass the test), the result must be at or below 98 ug/m3. Payson passed the motor 

vehicle test at 75.7 ug/m3, using a ten-year vehicle miles travelled (VMT) projected increase of 

23.8%. This VMT projected increase was based on Arizona Department of Transportation 

(ADOT) data for Gila County, where Payson is located. However, we note that since the LMP 

Update was submitted, ADOT’s VMT data was revised downward, resulting in even less VMT 

projected growth over the next ten-year period than ADEQ assumed in the LMP Plan Update.14

 

11 Memo to File, Nancy Levin, July 2, 2013 Conference Call with John Englander, ADEQ, response to question #4.

12 Ibid., response to question #5.

13 Limited Maintenance Plan Option for Moderate PM10 Nonattainment Areas (LMP Policy), Lydia Wegman, EPA, 

Director, Air Quality Standards and Strategies Division to EPA Regions I-X, Attachment B: Motor Vehicle 

Regional Analysis Methodology, August 9, 2001.

14 See ADOT website at http://mpd.azdot.gov/mpd/data/hpms.asp.